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Thread: Pro comp cylinder head question

  1. #1
    Daytona100
    Do,s anybody know the part number for some Manley valves to fit these heads? Calls for 2.25 + .250 on the intakes and 1.880 + .150 or .100 on the exhaust. 11/32 stems. Want to get some extreme duty intakes and some inconel exhaust valves. Anyone have any hands on experience assembling these heads? Big block Chevy. Thank you Mike.

  2. #2
    pw_Tony
    You've asked a 1000 times about these heads, I think you get the gyst of how some people feel about them. Good luck trying to get a straight answer lol

  3. #3
    Daytona100
    You've asked a 1000 times about these heads, I think you get the gyst of how some people feel about them. Good luck trying to get a straight answer lol
    Read the question!!! I want some part numbers thats all!!!!!! Thank you for your concern. Mike

  4. #4
    Jetaholic
    Do,s anybody know the part number for some Manley valves to fit these heads? Calls for 2.25 + .250 on the intakes and 1.880 + .150 or .100 on the exhaust. 11/32 stems. Want to get some extreme duty intakes and some inconel exhaust valves. Anyone have any hands on experience assembling these heads? Big block Chevy. Thank you Mike.
    First you gotta know what the installed height of the springs you're running is. That will tell you how long of a stem you need.
    As long as you get valves with the correct head and stem diameter they should fit the heads fine.

  5. #5
    pw_Tony
    How is one supposed to know the installed height is if you don't have valves yet? :idea:
    I think he has a bare set as well

  6. #6
    Jetaholic
    How is one supposed to know the installed height is if you don't have valves yet? :idea:
    I think he has a bare set as well
    Installed Height is a spring spec, not a valve length spec.
    When you buy a set of springs, they are designed to be installed at a certain height. This is the proper height of the spring that will give the correct amount of seat pressure, and is controlled by the length of the valve stem. If the valve is longer than the rated installed height of the spring, there will not be enough seat pressure and your valves won't seal to the seats, causing major compression and valve float issues. If the valve is shorter than the rated installed height of the spring, the spring will apply too much seat pressure to the valve, which will cause the valve to beat the shit out of the seats. It can also cause a flat tappet cam to go flat by making it harder for the cam lobe to open the valve. On a roller cam, too much seat pressure can ruin the roller axles on the lifter, and cause a hydraulic lifter to blead down.
    Other issues with having too short of a valve stem will be incorrect valve train geometry and excessive coil bind.

  7. #7
    Daytona100
    Springs are comp 924-16 installed ht 1.880 Thank you mike

  8. #8
    Jetaholic
    You'll have to call Pro Comp on this one. Tell them which heads you have and what the installed height of the spring you're running is, and they should be able to tell you what length of stem you need.
    Another option is trial and error. Order up a set of valves, put one in the head and measure from the bottom of the spring cup to the top of the retainer locks...that measurement should equal the installed height of the spring. If it's too long or too short, figure out what the difference is and either add or subtract from that to figure out the correct stem length.

  9. #9
    VAMI
    intake 11856-8 exh 11737-8 thats a severe duty ex

  10. #10
    fc-pilot
    Manley inconel exhausts are 11737. That is for individual valves. The -8 might be what you need to order a set of eight. By the way, don't mess much with valve length. The heads are setup and machined to have rocker geometry proper for a tight range of valve length. You can always shim your springs to be at the right installed height.
    Paul

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